Is metal hyperaccumulation occurring in ultramafic vegetation of central and southern Mexico?

Properties of the subduction system in Mexico

Central and southern Mexico represents a strategic place to understand the dynamics of Pangaea break-up and its influences on the evolution of the Pacific margin of North America. Lower–Middle Jurassic volcano-sedimentary successions, and scarce magmatic rocks, crop out discontinuously across this region and have been interpreted either as a vestige of a continental arc or as several deposits of syn-rift magmatism. At present, their origin is controversial. Available geochemical data on these igneous rocks suggest that they represent almost pure crustal melts produced in a rift environment rather than in an arc. In fact, the studied rocks exhibit the high silica contents and moderate to strong peraluminous character typical of sediment melts. The enriched isotopic composition (high86Sr/87Sr and low143Nd/144Nd) and the age distributions of inherited zircon grains readily identify the widespread Upper Triassic metasedimentary sequences presently exposed in southwestern and central Mexico as the most likely crustal source of these Jurassic igneous rocks. Accordingly, we argue that these Early–Middle Jurassic magmas originated in a syn-rift igneous province associated with extensional-driven crustal attenuation in the context of Pangaea fragmentation. Our findings also constrain post-Pangaea subduction initiation to be younger than Middle Jurassic time in central and southern Mexico.

Distribution of hydrous minerals in the subduction system beneath Mexico

Biomass burning from grassland, forests, and agricultural waste results in large amounts of gases and particles emitted to the atmosphere, which affect air quality, population health, crop development, and natural vegetation. Regional atmospheric circulations can transport those plumes of pollutants over hundreds of kilometers, affecting vulnerable environments such as those considered protected natural areas (PNAs). This study evaluates the spatiotemporal distribution of active fires detected, and associated emissions, in central and southern Mexico from satellite data between March and June 2017, to assess the impact of the smoke plumes on protected ecosystems. The arrival of smoke plumes to selected PNAs (both near large urban centers and in remote areas) is assessed using airmass forward trajectories from selected emission sources. The spatial distribution of the remotely derived aerosol optical depth confirms the regional impact of particle emissions from the observed fires on PNAs, particularly in central Mexico. The identified areas of high fire density are also associated with large coarse particle concentrations at the surface. Moreover, there is a significant contribution of organic carbon to the total coarse particle mass, 60% on average. Finally, while most of the impact in ambient pollution is observed in PNAs located close to the regions with active fires in southern Mexico and Central America, the long-range transport of smoke plumes reaching the USA was also confirmed.

Mesozoic tectono-magmatic evolution of Mexico: An overview

This volume furthers our understanding of key basins in central and southern Mexico, and establishes links to exhumed sediment source areas in a plausible paleogeographic framework. Authors present new data and models on the relations between Mexican terranes and the assembly and breakup of western equatorial Pangea, plate-tectonic and terrane reconstructions, uplift and exhumation of source areas, the influence of magmatism on sedimentary systems, and the provenance and delivery of sediment to Mesozoic and Cenozoic basins. Additionally, authors establish relationships between basement regions (sediment source) in the areas that supplied sediment to Mesozoic rift basins, Late Cretaceous foreland systems, and Cenozoic basins developed in response to Cordilleran events.

This chapter provides a glimpse of the native experience in central Mexico since independence. Before independence, many legal and historical documents relating to central Mexico were still written in Nahuatl, and native litigants could present their cases in their own languages. Between independence and the present, most native peoples were culturally absorbed into a more Europeanized, Spanish-speaking nation. At the time of independence, many native people in both central and southern Mexico were members of former Indian republics or native pueblos, with their own land base and separate administrative structures. The social structure of native pueblos, throughout Mesoamerica, is usually depicted as a closed corporate community. Going back even before Mexican independence, the struggle of native peoples for land has been intrinsically related to legal battles in the courts, ideological debates, and armed rebellion. The logic of native political participation takes on a different form during times of relative political stability on the national level.

The Euphorbia adiantoides complex is here considered to consist of four species. This group is readily distinguished from other New World Euphorbia by the combination of two unusual features: entire styles with capitate stigmas and dichasial bracts with relatively long, filiform stipules. Euphorbia sonorae is reduced to a synonym of Euphorbia adiantoides, a taxon disjunctly distributed between Mexico and western South America. The other species of the complex are all restricted to Mexico. Two of these are described as new: E. zamudioi, an endemic to the Sierra Madre Oriental, and E. breedlovei, which is widespread in central and southern Mexico. A key to distinguish the species is provided, as too are data concerning their morphology, distribution, habitat, phenology, common names, and uses. Phylogenetic analyses were conducted using the nuclear ITS and the chloroplast psbA-trnH regions and including multiple samples of each species. The phylogenetic results are not always congruent with morphology, and of the four species herein recognized, only Euphorbia zamudioi is suggested to form an exclusive, well-supported lineage. This species is nested within E. breedlovei, and two collections of E. breedlovei from central Mexico are more closely related to E. zamudioi than they are to other E. breedlovei from southern Mexico. We hypothesize that E. zamudioi arose through peripatric speciation, in which a northern population of E. breedlovei became reproductively isolated and morphologically differentiated from the remainder of the populations of E. breedlovei.

The 3DVp,Vp/Vs, P‐ and S‐wave attenuation structure of the Cocos subduction zone in Mexico is imaged using earthquakes recorded by two temporary seismic arrays and local stations. Direct P wave arrivals on vertical components and direct S wave arrivals on transverse components from local earthquakes are used for velocity imaging. Relative delay times for P and PKP phases from teleseismic events are also used to obtain a deeper velocity structure beneath the southern seismic array. Using a spectral‐decay method, we calculate a path attenuation operatort* for each P and S waveform from local events, and then invert for 3D spatial variations in attenuation (Qp−1andQs−1). Inversion results reveal a low‐attenuation and high‐velocity Cocos slab. The slab dip angle increases from almost flat in central Mexico near Mexico City to about 30° in southern Mexico near the Isthmus of Tehuantepec. High attenuation and low velocity in the crust beneath the Trans‐Mexico Volcanic Belt correlate with low resistivity, and are probably related to dehydration of the slab and melting processes. The most pronounced high‐attenuation, low‐Vpand high‐Vp/Vsanomaly is found in the crust beneath the Veracruz Basin. A high‐velocity structure dipping into the mantle from the side of Gulf of Mexico coincides with a discontinuity from a receiver functions study, and provides an evidence for the collision between the Yucatán Block and Mexico in the Miocene.

A major provenance change in sandstones from the Tezoatlán basin, southern Mexico, controlled by Jurassic, sinistral normal motion along the Salado River fault: Implications for the reconstruction of Pangea

Seed and endocarp traits as markers of the biodiversity of regional sources of germplasm of tejocote ( Crataegus spp.) from Central and Southern Mexico

-I examined hypotheses of Aphelocoma jay phylogeny derived from allozyme data. Results from various algorithms differ in details, but the overall patterns are consistent: Scrub Jays (A. coerulescens) and Unicolored Jays (A. unicolor) were derived independently from different populations of Gray-breasted Jays (A. ultramarina). Within Scrub Jays, the californica subspecies group was derived from the populations of interior North America (woodhouseii group). One Unicolored Jay population and two Scrub Jay populations, all strongly differentiated, are placed consistently at the base of the phylogeny, but phenotypic, biogeographic, and theoretical evidence suggests that these populations represent rapidly evolving populations derived from within populations of their respective species. Because analyses of rates of evolution demonstrate significant rate heterogeneity, I suggest that the application of a to date-splitting events in the Aphelocoma jays is not a valid approach. Received 18 February 1991, accepted 3 July 1991. THE THREE species of Aphelocoma jays range throughout western and southern North America and northern Central America (Fig. 1; Pitelka 1951). Scrub Jays (A. coerulescens) range from Oregon and Wyoming south to the Isthmus of Tehuantepec, with disjunct populations on Santa Cruz Island off the coast of southern California and in peninsular Florida. The 15 subspecies form five groups, each characterized by unique combinations of plumage, morphological, and behavioral characters (Fig. 1; Pitelka 1951, Peterson 1991a): (1) woodhouseii group (Wyoming and southeastern Oregon south through Great Basin and along both sides of Rocky Mountains, and then along interior slopes of Sierra Madre Oriental and Sierra Madre Occidental of northern Mexico to southern Chihuahuan Desert and vicinity of Mexico City); (2) californica group (western Oregon, California, and Baja California); (3) sumichrasti group (southern Mexico); (4) coerulescens group (peninsular Florida); and (5) insularis group (Santa Cruz Island). The Gray-breasted Jay (A. ultramarina) ranges throughout the mountains of northern and central Mexico and the southwestern United States. The seven subspecies fall into three groups characterized by unique combinations of morphological and behavioral characters (Fig. 1; Pitelka 1951): (1) potosina group (Sierra Madre Oriental); (2) wollweberi group (Si' Present address: Department of Zoology, Field Museum of Natural History, Roosevelt Road at Lake Shore Drive, Chicago, Illinois 60605, USA. erra Madre Occidental); and (3) ultramarina group (Transvolcanic Belt). Finally, the Unicolored Jay (A. unicolor) consists of five allopatric populations, each a separate subspecies, in southern Mexico and northern Central America (Pitelka 1951). The Aphelocoma jays have been the subject of numerous comparative studies. Evaluations of social systems in the genus have led to advances in understanding ecological factors important in the evolution of sociality (Woolfenden and Fitzpatrick 1984, Fitzpatrick and Woolfenden 1986, Brown 1987, Peterson and Burt, in press). Differential habitat use in Scrub Jays (Peterson and Vargas 1992) is correlated with geographic variation in beak shape, suggesting that beak shapes have responded to natural selection (Peterson, in prep.). Integration of phylogenetic information into such investigations will allow an important new dimension of understanding (Brooks and McLennan 1990). Hence, I have attempted to estimate the phylogeny of the differentiated forms in the genus. Rates of evolution. -Since the publication of the influential paper of Zuckerkandl and Pauling (1962), the idea of a molecular clock has been controversial in biology and systematics. The concept is based on the assumption of a uniform rate of evolution in a group. If the uniform rate assumption were correct, the accumulation of genetic differentiation between sister taxa would be time-invariant, and divergence times could be estimated from genetic distances. The concept is an important feature of

Deep crustal structure of central Mexico derived from interpretation of Bouguer gravity anomaly data

The ancient city of Teotihuacan was a great urban and ceremonial center, whose population grew exceptionally in the Classic Period (300 – 700 AC). Settlement patterns, culture and burials have indicated an occupation that consisted of groups of neighboring apartment compounds or barrios. We investigated the genetics of three apartment compounds in the Teotihuacan Valley through ancient DNA analysis to prove multiethnicity during the Classic Period. Amerindian mitochondrial haplogroups were identified in 10 burials from San Francisco Mazapa, 7 from San Sebastian Xolalpan, and 19 human bone tools from La Ventilla. These samples had a wide genetic diversity. Differences in genetic structures were slight but significant (p< 0.001) between the three households and 7 ancient populations from Central and Southern Mexico by FST analysis between the three barrios studied, and Xaltocan (post-conquest) was congruent with the number of migrants estimated. Tlailotlacan, another household of Teotihuacan, was different following a small interaction with Mazapa, Xolalpan and La Ventilla. Through the estimation of immigrants, the three households studied seem to have come into contact with Mayans from Xcaret in Yucatan, and this coincides with archaeological data reported. Genetic data could indicate that migration and less genetic drift may possibly lead to a more effective role in the Teotihuacan groups, suggesting that interchange with other groups was not only for commercial, service or governmental purposes, which implicated demographic integration and genetic fusion, culminating in multiethnicity during the Classic Period in Teotihuacan. Further studies can be directed to examine others households.

The widespread but endemic mud turtle species Kinosternon integrum Le Conte, 1854 currently ranges throughout most of Mexico, from southern Sonora in the northwest to and through western, central and southern Mexico at least to eastern Oaxaca. Broad and convincing evidence indicates that Kinosternon integrum actually represents a taxonomically complicated species complex; however, as the holotype has allegedly been lost for more than a sesquicentennial and the specimen’s original collection locality data is lacking, a comprehensive systematic revision of the original concept of the species is required before convincing taxonomic subdivision of the complex can proceed. In this contribution we designate a neotype specimen, drawing from the species junior subjective synonym Cinosternon rostellum Bocourt, 1876 and subsequent junior objective synonym Cinosternon guanajuatense Dugès, 1888. We review nomenclatural history and application, argue for the ambit of locality data of the lost holotype collected during the Mexican-American War (1846-1848) and provide a sensu-stricto morphological redescription of, K. integrum based on the museum accessioned and living specimens documented throughout the range. Even though this study now confines its distribution to the majority of states within central Mexico, K. integrum retains its honorific of the most vagile and widely distributed mud turtle in the country.